Semi-automatic telephone-exchange system.



, AF. n.' M'CBERTY. SEMI-AUTOMATIC TELEPHONE EXCHANGE SYSTEM..

i APP-LlCATIQPJI FILED SEPT.I3.19I2. 1,284,996. l PatentedN0v.19,1913.

8 SHEETS-SHEET l.l

F.- n: Mesem.4 SEMI-AUTIOMATIC TELEPHONE EXCHAGE SYSTEM. APPLICATIONFILE D SEPT. I3. I9| 2.y

1,284,996. .Patented L\"0v. 19,19^18.l

V s Sums-slim s.

j' Affy.

APPLICTIOILFILED SEPI. I3, ISI?. V -l Patented NOV. 19, 1918.

F. R. McBERTY. sEMLAuToMAnc TELEPHONE EXCHANGE SYSTEM.

APPLCATION FILED SEPTJS, |9I2.

Patented Nov. 19, 1918.

8 SHEETSSHEET 5.

lll/V/'nessesx @291, infra,

` Y r. n. mamy. SEMI-AUTOMATIC TELEPHONE EXCHANGE SYSTEM. APPLlc/mon msosur. la, m2.

1,284,996.- Patented N0v.19,191&

W/fnessesf Y l /n yen for.' 0. En. @Jr/L Ffm/f Mceffy.

A F. R. MCBERTY. SENT-AUTOMATIC TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED SEPT. T3. l9l2. .1,284.996.l PatentedN0v.19,1918.

s SHEETS-SHEET 7.

kF. II. MCBEIIIY.,

SEMI-AUTOMATIC TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED SEPT. I3. I jIz.

- 1,284,996. Patented Nov. 19, 1918.

8 SHEETS-SHEET 8.

LKFI WIFI FIFIFIIFIIFI@ @III *IWL-g f UNITED sTATEs PATENT oEEIcE.

FRANK R. MCBERTY, OF ANTWERP, BELGIUM, ASSIGNORyBY MESNE ASSIGNMENTS, TOWESTERN ELECTRIC COMPANY, INCORPORATED, A CORPORATION OFNEW YORK.

SEMI-AUTOMATIC TELEPHONE-EXCHANGE SYSTEM.l

Patented Nov. 19, 191s.

Application led September 13, 1912. Serial No. 720,169.

To all fw hom t 'may concern.'

Be it known that I, FRANK R. MOBERTY,

a citizen ofthe United States, and a resident of Antwerp, in theProvince of Antwerp and Kingdom of Belgium, have invented new and usefulImprovements in Semi-Automatic Telephone-Exchange Systems, of which thefollowing is' a specification.

This invention relates lin general to improvements in telephoneexchangeV systems for the interconnection of telephone lines, and has todo more particularly with systems in which the extension of the desiredconnection from a calling line to a called line is accomplishedbyautomatic selector switches, under the control of an operator at thecentral or switching station. Certain features to be described, however,are not restricted to systems of this character, being also applicable,as will be apparent to those skilled in the art, to systems of widelyvarying character, as, for example, to full automatic telephone exchangesystems and, particularlythose features relating to the connection of acalling line with an operator, to manual telephone exchange systems.

One of the principal features of the invention has todo with theassociation of an operator with a connection to be Vextended for thepurpose of receiving the instructions from the party calling, inaccordance with which she will then act to produce the desiredconnection. To produce the best results in a system of this character,it is necessary thatmore than one operator should be able to control theestablishment of any desired connection. For this purpose the in-vvention involves the distribution of calls to home or alternateoperators, it being possible for either a home or alternate operator tocontrol the establishment of any desired connection. In this system ofdistribution,

prepared to receive a call and establish thel desired connection, suchcircuit to be extended will be associated with such alternate' operator.The inventlon, therefore, may be idle, but if such operatorris-not idle'being automatically associated with some other operator.

A further feature of the invention relates to the automatic distributionof calls, thlatl is, of circuits to be extended, notgonly to operatorsbut also to one of a plurality of controlling equipments individual tosuch operator. A call coming in causes first the automatic selection ofan idle'operator, and then the automatic selection of an idle con#trolling equipment of 'such operator, such selection causing theassociation with the circuit to belextended on` which suchl call hascome inaof the equipment for controlling the establishment of thedesired connection. l I Another feature of the invention provides meanswhereby every call coming into .a

semi-automatic exchange, in which calling lines are automaticallyconnected to an 'operators position and are connectible to such,operatorif idle, will be indicated before such operator by a visualsignal, such visual signal, although located on one operators position.being observable by a plurality of operators, any one of which mayobtain access to the circuit to which the signal is individual, for thepurpose of controlling the extension of the desired connection.Furthermore, the invention provides that all calls in the exchangeconnected to any operators position, and still unattended to, aresimultaneously indicated. each by its own visual signal, so that at alltimes the number of calls awaiting attention will be apparent to eachoperator, and to the other operators to whom the circuits on which suchcalls have been received are accessible.

' A further feature of the invention provides that a circuit to beextended, having caused the selection of an idle operator and of an idleequipment of such operator. will.

be connected to the telephone of such operator and to such controllingequipment by separate and independent leads. B v such arrangement it ispossible that, as soon as the operator has received the necessaryinstructions from the calling party, and has out the necessity. ofavvaitmgi the completionv of the operation of the one of her controllingequipments used, her telephone being 'automatically connectible to acalling line, together with an alternate. equipment, as soon as itbecomes idle.

In the invention another feature provides not only the automaticconnection of an operators controlling equipment to a circuit to beextended for the purpose 'of controlling the extension of such circuitto the desired line over automaticselector switches, but also providesfor the automatic disconnection of such controlling equipment from lzosuch circuit at the very earliest stage in theV connection at which suchdisconnection can properly take place; That is to say, one of thefeatures of the invention relates to the automatic 'disconnection of thecontrolling equipment immediately upon the selection in the final-selector switch,y of the set of terminals in correspondence with thenumerical I designation of which. the controlling equipment has beenoperated, such automatic disconnection taking place before the testingof the line associated with such terminals, before the ringing of thelineif such line is idle-and before the response ofl the calledsubscriber. In accordance with this feature of the invention,the time ofuse of a controlling lequipment in connection with any selectingoperation is materially shortened, the circuits for testing,ringing,'and the establishment of the talking' connection in response tothe reply of the called subscriber being purely local, and in no wayrequiring ling equipment.

-According to the invention, furthermore,

although each connection is established over automatic selectorswitches, and also preferably over automatic line finder or distributingswitches, the operator, to whose position the connecting circuit overwhich the call has been extended is individual, has at all times access`and complete control over the hconnection established, or beingestablished. For this purpose, the invention provides that eachconnecting circuit shall appear before the operator in a requisite num-'l ber of signal lamps and controlling keys,

whereby the operator 'may supervise the conthe assistance, or direction,of the controlnection at any time, and lin any way desirable. n

Another feature of the invention, -and relating particularly tosemi-automatic systems, in which supervision of the call established'orbeing established is always ossible, relates to the -fact that the estab1shment of the call-that is to say, the receipt of the necessaryinstructions from the calling party, the bringin about of thenecesvisedby another operator.-

Another feature of the invention relating to systems in which lthecallis established over automatic selectorswitches, but havingbeenestablished is su ervised by an operator at the central o ce, providesthat the complete disconnectionl of an established call,- involving therestoration 'to normal condition of all of the apparatus forming part ofsuch connection is controlled by manually operable means #before thesuper- `vising operator, and in thetparticular form shown herein residesin a single manually operable key individual to the connecting circuitover which such call is established.

It sometimes occurs that it Ais desirable that a connection, beingestablished or fully established should be maintained, While at gie.same time it is desirablethat' the line so onnected should be free tocall and be called in the normal manner. A feature of the invention,therefore, relates -to holding the 'switches in the position towhichthey have been brought for inspection or other. purposes, while, atthe same time, causing 4the subscribers line, or subscribers linesattached to such connection, to be freed entirely at the line finder orfinal selector, the brushes of which rest upon the terminals thereof, sothat such line or lines m'aycallor be called in the normal manner. Asshown the means for accomplishing this holding condition, may compriserelays under the control of manually operated means before thesupervising operator, which relays in turn control the apparatusassociated with the switches forming the extremes of the connection.

Other features of the invention have to do with the circuits andoperation of the line finderswitches by which the idle connectingcircuit is brought into connection with a calling line. One of thesefeatures provides a pilot relay under the control of any line of agroup, whereby' all the idle line finders in which such group of linesterminate will immediately start to searchl fora calling line. Thecircuit by which the pilot relay is energized also forms one of thefeatures of the invention. This circuit, controlled by a single contactdevice," provides ,when closed, not only the energizing circuit for thepilot relay itself, but by nzeans of a branch therefrom, places aselectable poten-1 tial upon the test termina-l of the calling line in`all the finder switches in which such line appears, From anotherstandpoint this circuit may be considered as, in part, a coinmoncircuit, in whieh'part .the pilot relay common tol a groupV of lines islocated, and in part comprising an individual circuit for each of thelines of such group, the estaba line in such a manner that the properpotential will exist upon the test terminal of such line when calling,until suchline has been seized by a line finder switch, at which timethev potential upon such test terminals will be so changed thatno otherone of the line finder switches in which such line appears will be ableto seize such line, and fur- -thermore, that the potential or changedpotential upon the test terminal of one line will have no effect uponthe potential, lack of potential or change of potential on the testterminals of another line o f such group, even though the source ofpotential for such test terminals is in the common portion of suchcircuit.

Another feature of the invention involves `the vuse in line finderswitches, of means whereby immediately upon the brushes of a line finderswitch coming` in contact with the terminals of a calling line ai testguard will be placed upon Ythe test terminals of such line, in all otherline finder switches in which it appears, to prevent its seizure by anyother of such line finders, whereas,

the motion of the seizing line finder will not be arrested until thebrushes thereof are properly centered upon the terminals of the line.`This is accomplished by locating` in the test circuit two relays, one ofthem operating immediately upon the brushes coming in contact with theterminals of the calling line to place the test guard thereon, and theother operating subsequently, upon the opening of a local interrupterdevice carried by the line finder switch, to arrest the motion of suchfinder switch. Another feature relates to the subsequent transference ofthe test relays located in such test circuit-one to an alternative testcircuit and the other to a controlling ci'rcuit whereby the restorationof the line finder apparatus to normal may be controlled; as desired. if

Another feature of the invention, relating particularly to systems inwhich a/calling line is connected to an idle connecting circuit Athrougha plurality of line finder switches, provides tliatfwhen a calling linehas been seized, and connected to by a first line finder switch, all ofthe idle second line finder switches in which appears the cir- Acuitindividual to the first line finder switch to which the line is nowconnected` will startv in motion to hunt, and one of them seize suchcircuit, whereby the calling line will'be extended to the connectingcircuit individual to the` seizing second line finder switch. Related tothis feature is another feature of this invention, according to whichthecontrol of the starting in motion of such idle second line findersresides in a sequence switch (steering switch) individual to the firstline finder, whereby the seizure of the calling line by the first linefinder iminedilately initiates the operation of such sequence switch,resulting in the starting in motion of the idle second line finders inwhich such first line finder is accessible.

Another feature of the invention, and relating particularly to systemsin which a ,calling line is connected to an idle connecting circuit byline finder switches is embodied in the provision of line finderswitches the brushes of which have no normal position and move in onedirectionv only. Upon the seizure of a calling line by one of' aplurality of moving line finder switches, all of such switches will,provided no other line is at that time calling, immediately stop inwhatever position they may respectively be in, and having stopped, willremain in such position until the establishment in some other line ofthe group of lines terminating in such switches, of a calling condition,at which time they will again start in motion and continue therein untilsuch line is found.

A related feature of the invention provides that when the brushes of aline finder switch ,rest upon the terminals of a line in which a"calling condition is established, such line finder switch Wlllimmediately seize such line Without any movement of its brushes, andprevent the seizure of such line by any other line finder switch.

Another feature of the invention relatingl to systems in which a callingline is connected to an idle connecting circuitl throughv a plurality ofline finder switches provides that the restoration of the first finderswitch through which a connection has been established is dependent onthe condition of the Second finder switch which has formed a of the sameconnection. It further prov ides that upon the initiation oftherestoring operationin such connection the apparatus o,

or` becalled inthe normal manner, but the ffapparatus'of such firstfinder switch will be, Amaintained in an off-'normal pos1tion,to

,prevent the use of such first finder switch in asubsequent connection,until theapparatus offthe second finder switch connected with vit,'anditsconnecting circuit, have been restored to their normal condition.

Other features of the inventionhave to do with the use, location, andoperation of s equence'switches (steering switches) 1n various portionsof a telephoney exchange system, for controlling various portions of theapparatusand-fthe controlling and extension of the various circuits.Forexample, one ofthe features of the invention'relates to the use of asequence switch for-controlling the first y, line finder.

Another feature relates to the use of a se- Iquence switch common to andcontrolling of a plurallty of o A further featurev relates tothe use ofthe both the second line finder switch and the oup selector. Anotherfeature relates to t e use of a sequence switch .to determine theselection by a calling line of an idle operator rators .to any one ofwhich such calling e may be connected.

same sequence switch for controllingnot only the selection' of anidleoperator but also 'the l selection of an idle controlling-equipmentof the operator selected. Still another feature of the .invention rellates to the use of a plurality of electromech- 40 anisms (herein shownas sequence switches) to accomplish the selection and extension ofa'circuit to a. particular one of a plurality of circuits, in suchselection the circuit extend-A ingl mechanism (group. sequence switch)understood .that while', for the sake of clear-v switch).

5 l v l u 4 mvention w1ll sullclently appear from vthemaintaini thefirst said circuit open, but closing. suc circuit when the desired se-Vlection has been accomplished bythe circuit choosing mechanism (positionsequence Other novel and important features of the detailed descriptionthereof, and it will be ness specific descriptive language must be usedin describing the embodiment of the invention shown herein, such languaeis not to' be construed as un any-.way limiting'the invention, sincethe various features thereof may appear in widely varying and dissimilarforms when used-in other systems than the specific one herein described.

A. system embodying the .invention is diagrammatically illustrated inthe`drawings in whichigure l shows the calling substation and y .the firstfinder switch will be so operatedthatthe subscribers line to which itisconnected will be immediately freed to call 4the controlling .-of Fig.l,

v sidin accompanylinei'and the` circuit of the first line Figs. 2 and'2; show a connecting circuit vand the secondfinder switch and groupselector associated therewith.

. Fig. 3 shows the line or final selector and A the substation'circuit of lthe called line.

A F ig, 4 shows the circuits of two operators" f s uence switches'.`

a whole, F1

he ground `and final selectors areof the multiple brush -type, describedin the British Patent N o. 20841/09, in which the brush carriage isdriven by constantly supplied power coupled thereto when needed througha magnetic-.clutch andcarries brushes heldfree of the terminals lbylatches any one of which may be withdrawn to allow its set of brushes tomake contact successively with thesets of terminals individual thereto.

The set of brushes is chosen by a tripping spindle` according to thedifferent angular positions thereof, which is driven by the same-constantly supplied poweras the brush-carriage with which it through amagnetic clutch. i

The line `linder switches shown at and `200 are somewhat similarin-construction to the selectors, the principal differences reset o`brushes mounted on the brush-carriage, and such brushes are normally inposition to make'contact with the sets `of contact terminals o ver whichthey pass. Furthermore, the line lnder switches have no normal positionand, having been moved'in hunting acalling line, remain in' suchplosition' until subsequently again taken In bothth limanda` swiahes andthe selectors the;,top of thet'brush-carriage carries an interrupterwhich inter-acts with a` toothed rackupon the frame of its switchinfsuch a way that'a circuit isv established to maintain thebrush-carriagev in motion whenever the brushes are passing from one setof terminals to the next. When the is associated,

in'that they each have but a single brushes are properly centered upon aset of terminals, however, this circuit 1s open and the movement lof thebrush-carriage will sto wit a set of contacttermmals.

Thesystem shown also utilizes electro'- l'rnagnetic switchingy devicesknown as sewith the -brushes squarely in contact l vqhence switches.Devices of this character the British Patent No.

' quence switch in which any of its contacts are indicated by `suchcontacts, each be vunderstood that the special contact 111" (except thecontacts corresponding to 111 of the line finder sequence switch) areclosed, numbers placed adjacent to" A contact being open in allpositions except those indicated by such reference numerals. Forexample, contact 58 top is closed in the fourth and from such positionthrough the seventh position of the line finder sequence switch'of whichit forms apart as indicated by the Anumbers 4-7 adjacent thereto, andthe alternate or bottom Contact is closed in the first and secondpositions, as indicated `by the gures 1, 2, adjacent to such alternatecontact, said contact being open in all positions except those soindicated. In the case of the special contacts such as 111, thenumbers-are placed on the opposite side of the switch lever from itsContactpoint and indicate positions in which the 4Contact is opened,such contact being closed continuously while the rotary elementoffsequence' switch is in transit between positions indicated. It willtherefore of the sequence switch105 is closed continuously betwenpositions 1' and 4, 4 and 5, 5 and 7, and 7 and 1, but is opened whenthe sequence switch is either resting in or passing through any one ofthese positions.

A In the system herein disclosed, the operator receives the number fromthe subscriber and then manipulates keys which serve to set in operationmechanism adapted to eX- tend the connection automatically to thedesired line and these keys are divided into 45.

four setsof ten each for the thousands, hundreds, ltens and unitsrespectively, These keys are shown diagrammatically in'Fig. 6. Theoperator having received the number of the desired line presses a key ofeach set corresponding to digits of the number desired. locked downwhenV depressed, and remain in such condition until the magnets aredenergized.

There are provided at each operators position two duplicate senders. Aand B, each controlled by a sequence switch 505, and

each comprising twentv-pairs of counting relays 179, 180 and fourregisters whose power magnetsare designated 160, 161, 162, and 163, andbelongto the thousands, hundreds, tens and units registers respectively.

o In general, lthe register is a sequence switch having the usual powermagnet and the usuall contacts operated/by cams, located on revolvetheir shafts, and wh contacts on the registers corresponding to The keysare electromagnetically the sequence switch shaft. The only difcontactsof which are connected with the thousands keys. It has in addition aspring 191 shown below.

` The hundreds register 161 has in addition to the five springs shownabove its power magnet, the coperating contacts of which are connectedwith the springs of the hundreds keys, five springs numbered 183, 187,and ve springs numbered from 192- 196; also spring 197.

The tens register, has in addition to the tive springs, the contacts'ofwhichare connected to the tens keys, five springs numbered 1883-1871.

The units register has inLadditio'nfto the five springs, the contacts ofwhich are con nected to the units keys, tive springs numbered 192b-196.

In general it may be stated that when the register power magnets areenergized, they n the upper the keys depressed' b'y the operator arereached, 'circuits are closed through the stop relays 17 0-17 3 whichcut O'the powerfrom the register and stop it revolvingwith the uppercontact closed. in each corresponding to the depressed key. The lowersprings of the registers are .closed or open as indicated by theposition numbers adjacent thereto according to the set position of theregister as determined by the upper springs and such lower springscontrol the operation of the counting relays .which themselves determinethe number of stepsthat the various selectors are to take in theiroperation to eX- tend the connection to the desired line.

The operator isprovided'1 with the usual telephone set (not shown) whichis connected to the conductors leading from the lower contacts ofsequence switch springs 90-91 (Fig. 2). The upper contacts of the samevsequence switch springs lead to the telephone set of the operatorlocated to the i left; who may assist the home operator. This operatorwill be referred to as anv alternate operator. The operators telephoneset is also connected to the conductors leading from the springs butthese connections are also -`omitted-for the sake of clearness. This keyis to permit the operator to communicate with a sub-` scriber after hertelephone set has been automatically disconnected in the normaloperation of the system. The operator is also of the listeningl key 288,

a duplication o f the means for connecting the left handl operators set.

The subscribers set is of the kind usually provided in common batterymanual telephone eXcha'nges. The lines are connected to multipled.terminals in the banks of each of a group of rst line finder switches.

AThey alsov appear in multipled terminalsA of the proper n al selectors.There may be provided a smaller number of line finders than subscribers,and a still smaller number of second line finders (200) may be prvided,and o erate" substantially in the same way-'as the rst `line finder,each second line.

finder being connected with a group `switch Y connected to battery, thisfinder willstop ro4 associated with the grou It will be understoodthat'the sequencel switch springs inFig. 2 surrounded by the .dot anddash lines are associated with the position `sequence switch 305,whereas all those outside of the dot and dash linesv are sequence switch205, which latter contro s the line finder switch and 'group selector.

The system shown is best described by an lexplanation of the yoperationthereof. f

Assume that the subscriber whose sub- -stationis shownat 50on Fig. 1desires connection with the subscriber, the numerical designation ofwhose lineis 1149, and fura ther assume that such subscriber is the .one

whose substation is shown at 278 on Fig. 3. When the subscriber at'50removes the telephone from its hook, the line relay 51 (Fig 1) isenergized, and closes a circuit to energize the pilot relay 52. Thiscircuit also, by means of a branch leading oi between the resistance 53and the resistance 54, placed a selectableA potential on the terminal104 of the line finder 100, and of all the, other line* finders of thegroup in which this line appears. This pilot relay 52 is commonto suchgroup of line finders, and when energized, causes the.brush-.carriage'of all ofthe idle finders in the group to rotate, overcircuits includingrsprings 55 bottom, and 56 bottom, and brush-carriagepower magnet '106. A" group' of idle first -inder switches is nowhunting for the calling line,

the brushes traversing the line terminals- 101, 102, 103, 104, and whenthe firstv arriving line finder is fully centered upon the calling linewhose test terminal 104.has.been

tating due to the 'closure' of the circuit through relay 107 whichincludes spring 58 bottom', upper (highresistance) windingv of squarel104 by thecalling through two circuits in parallel, each of test relay108, spring 59 bottom, brush 104B, terminal 104, resistance 53 and relay52. The resistance of the` shunt circuit from resistance 53 throughresistance 54 to ground is so proportioned that sutlicient current willflow through relay 108 to actuate it. Relay 108 is energized beforerelay 107 due to the shunt about the latter closed by the interrupter109 whenever the brushes are not centered on the terminals, and inrespon ing closes at its front contact apath of low resistance throughits lower winding, so reducing the potential of the. test terminal 104and its multiples that no other relays 108 and 107 can be energizedthereby, and therefore causing the line to appearnoncallin to all otherline linder switches.l If

two -lme finders should reach the terminal 104 of a calling line at thesame time, the circuit from-'the battery placed on terminal line wouldbe closed which would contain relays 108 and 107. The two relays 108would lconsequently be simultaneously energized and generally-one of thetwo would close its armature contact first, by virtue of which thecircuit containing this relay, due to its decreased resistance, woulddraw the major part of the currentof the parallel circuit and the secondrelay 108 would therefore receive insufficient cur rent -to attract itsarmature. However, if

allel c ircuit would be so reduced that the potential difference at theterminals of the relays -would be so `small that the current traversingthe coils of the relays would be insuliicient to hold up the armaturesof both relays and one or the other would ydrop back.

When relay 107'is energized, it opens the circuit of the power magnet106 and closes a circuit to energize' the holding magnet 110 throughspring 55 bottom. At the same time relay 107 energizes the sequenceswitch power magnet 105 over spring 59EL and it moves from position 1 toposition 4, ,nfloving through positions 2 and 3 by reason of the closureof contact 111 in those positions. A ts the sequenceswitch moves throughposition 2 a circuit is closed over sprin 61 and the third brush 103'ELof the Aline fignder to operate the cut-oil; relay 62 which circuit byreducing the potential on the terminal 103, makes the 'seized line testbusy in all the final selectors in which it appears. The operation ofthe cut-oil' relay also connects the line conductors to the terminals101, 102 of 'the finder at the upper front contacts of relay 6 2,and,unless some other line ofthe group 1s call1ng, and has not as yet been-seized by aline finder, opens the circuit of the pilot rela-y 52 toarrest the'movement of any other line finders which may have beenseeking this line. At position 4 of the sequence switch 105a circuit isclosed over spring63 to a local wire leading to a group of second linefinder switches 2 00, in which the conductorsconneoted to the first linender switch 100 appear, causing the idle finders of such group to huntfor the first line finder now connected to the calling line.

The sequence switch 105 (Fig. 1.) at position 4 has prepared at'springs58 top and 57 top a circuit leading to the 4th terminal 204 of this linewhich will be closed when a second line finder switch "reaches saidterminal and will cause, by the energizationgof the relay 208, theinclusion in this circuit of a low resistance pathl to reduce thepotenstopped. Potential being present therefore.

- 67, normal contactlof locking key ond line finder over spring 71bottom and` position 1 into position 2, an impulse is tial of theterminal 204 to render it nonselectable 'to other second line finderswitches, and when the brushes have been squarely centered on terminalsleading to the calling first line inderswitch the brush-carriage is.upon test terminal 204, upon the test brush 204aarriv1ng thereat, therelay 208'to ground l is immediately energized and a moment later whenthe ground at the interrupter is removed, the relay207 is alsoenergized'opening the driving circuit of the brush carriage and closingthe circuit for the holding magnet. It has also closed over spring 66bottom and spring 63 (Fig. 1) a circuit for the group sequence switch205. This sequence switch 205 therefore moves into position 2in whichmovement an impulse is transmitted to the irst finder sequence switch105, over left-back Contact of relay 199, spring 69 bottom, and spring70 bottom.

his sequence-switch is moved into position 5 in which .position thecalling subscribers line wires are connected through to the secsping 72bottom. The circuit of relay 107 of the lirstl finder remains closed atsprings 57 and 58 top (Fig. 1) and 65 bottom (Fig.

2) and consequently relays 2 08 and 207 (Fig. 2) and 107 (Fig. 1) remainenergized. This is a locking circuit and remains closed until 'theoperator` clears out the connection.

As the group sequence switch moves from also transmitted rto theposition sequence switch 305 over spring 73 top and spring 74 bottom,causing such sequence switch to move from position 1- into lposition .2,in

which position the test is made for -an idle operator.

In Fig.` 4 are shown two operators sei quence switches, one of which isvassociated with the home operatorzs position HP and the other withthealternate operators posi- 4tion AP, which` alternate operators positiononly comes into service when the home position HP is busy.

When the operators are on duty the hand 68, relay relay 82 at its frontcontact switches 75 and 76 at their respective positions are closed. i

When the position sequence switch 305 advanced into position 2, circuitsto the position test relays 77 and 78 were closed at spring 79 bottomand spring 80 bottom respectively, to the. home operators position andto the alternate operators position, through the respective handswitches 75 and 76 and the spring 81 top of the sequence switches ofsuch operators positions and over the back contacts of the relays 82 toearth. When, and only when, an operator is idle the spring 81 is closedat the top. -If both the operators should be idle at the moment when theposition sequence switch 305 reaches position 2, both the home and thealternaterelays 77 and 78 will be energized These relays establishholding cir- 'cuits from vthe power magnet 305 4over their frontcontacts, their' right hand windings and the windings of the respectiverelays 82 to earth. It will be first assumed that the home position HPwas idle, and that the alternate position was either engaged or that itshand switch was not closed.

)Vith the group sequence switch 205 in position 2, the position sequenceswitch 305 in position 2, and the home operators sequence switch 405 inposition 1, relay 7 7 will be energized by a circuit over spring 79bottom, hand switch 75, spring 81 top, and back contact of relay 82,whereupon it closes an energizing circuit for relay 82, i11- cluding.position sequence switch power magnet 305, spring 84 top, front contactof relay 77, right hand winding of relay 77, resistance 83, (Fig. 4) andrelay 82. The i closes a circuit by way of spring 85 for the homeoperators sequence switch, whereupon it moves to po.- sition 2, in whichposition the resistance 83 is short circuited by the closure'of springSti-bottom, with the result that power magnet 305 of the positionsequence switch will receive enough current to rotate the sequenceswitch to position 3. Inasmuch as it was assumed that the relay 77became energized,

the position sequence switch will move to position 7 since the circuitestablished remains closed until the position' sequence switch 305 Yhasrotated beyond position 6, when it will be opened at spring 84 top. Whenthis occurs the relay 82 (Fig. 4) is denergized, and a circuit is closedover spring 81 bottom, to energize themagnet 405 which thereupon movesthe home position sequence switch into position 3.

With the group sequence switch 205 in position 2, and the positionsequence switch 305 -in position 7, the home operators sequence switch405, as it starts to move from position 2 to position 3, will transmitan v'have'occurredif the alternate o erator hady been idle and herswitch 7 6 had een closed,- f the energizing of such relay would haveini.l

205 to move it into position 3. Before the group operators sequenceswitch fully arrives in position 3 thereof, an energizing.

circuit for relay 82 is closed through magnet 210 of the 2nd nder, frontcontact of 'relay 207 sprin 64 bottom, spring. 88 bottom, and

spring 87 ottom. This relay 82 is therefore energized-to maintainthehome operators sequence switch in position 3 and remains" energizeduntil the operator has recorded the ca l.

It shouldv be relay 7 8 had been energized simultaneously with the relay77 in the'second position of the` positionsequence switch, which wouldtiated a cycle of operations inthe alternate operators sequence switchAP, but since the l position sequence sw'itch, when it moved from itssecond position, was driven directly the relay 78 is the first to beenergized, or ifinto its seventhl position, no holding' or checkingcircuit would be established or maintained for the alternate operatorssel quence switch and it would return immediately to its normalposition.` y

On the other hand, assuming that the home operator is busy when theposition se- `quence switch arrives in position 2, the relay 77 will notbe energized as the circuit for it is `open at contact 81 of the homeoperators -sequence' switch'.l If at v-this time the alter-Anaten'operator .is also b usy, and, consequently, no 'circuit-isestablishedv for the relay 78, the

position sequence switchwill remain in p o sition 2 until a circuit forone or the other relays77 or 78 is closed. If the relay 77 is the firstone energized the circuit operation will be as .has been described; if,however,

Athe relay 78 was the only one energized when the position sequenceswitch came into position 2'the position sequence switch in response tothe operation of the alternate operators sequence switch, will move intopo sition4 3- where the same operation'will --take place-to drive thegroup sequence switch into position 3 response to the operation of thealternate .operators sequence switch as have been described as takingplace in position 7- under the control of thehome operators se- Iquenceswitch. Also the alternate operators sequence switch will be held in-position 3 in precisely the same manner that the home operatorssequence switch' was held inthe same position.

Furthermore,A it will be apparent that if when the position sequenceswitch comes into position 2 the switches 75 and 76 were both open, theoperation of the sequence switches .will be held up just as though bothoperators were busy and upon the closure of one of such switches, theoperation of such sequence switches will forthwith proceed to hereobservedtha't if thek menace extendtheconnecting' circuit to theoperator whose switch is closed. While,however, the

position sequence 'switch stands Vin position 2 the lamp 95 will becontinuously lighted indicating to both. the home operator and thealternate operator that acall'is awaiting attention, so thatat alltimesall of the opertois hayin access to any given connecting circuit anto which they are automatically connectible as described, will be s .bleto observe just how many calling lines 'are awaitingi attention.

eturning, however, tothe case assumed i' the group sequence switch .205is now' in .position 3,- the home operators sequence switch 405 is inposition A3 and the osition' sequence switch `305 is. in position The`home operators telephone set was connected across the line bytheclosure of springs 90 i and 91 vbottom when the position sequence switch'moved into position 7, Vcurrent for talking purposes being suppliedthrough springs 9 2 and 93 closed in this position.l It

will be noted that lthe calling and supervisory relay 94 is included invthis circuit` and that these springs areclosed )when the positionswitch arrives at position 2, thus lighting the lamp 95 in positions 2and 3 of the second finder` sequence switch for thev purposes described.Furthermore`there is a circuit 'closed through the progress'larnp 96 atspring top, thisV lam remaining lighted until the calledw subscri er hasanswered;

`that is, during the entire progress of the connection, and is .anindication to` the operator that a callis going. through on this trunk.v p l The operator noting the lighting of the calling lamp inquires thenumber desired by the subscriber.. In the meantime aselectioncontrolling equipment (Fig. 5) has been selected and seized inthe following manner: With they connectingcircuit, therefore,

`connected to the home operator, a test cir" 'cuit is established topick up the idle one circuit above referred to is continued to re' lay99, which is energized and establishes a circuit over spring 150 top,for first equipment sequence switch 505 and moves it into' position 2.The circuitV through the relay 99 and the position. sequence switch 305remains closed., until interrupted atfspring 84 bottom in position9,hence position sequence some earlier period equipment would Lass-,596 lswitch 305 assumes position 9, and the relay 99 at the controllingequipment becomes deenergized closing a circuit over spring 150 bottom,to drive the equipment sequence switch (505) into position 3.

As the equipment sequence switch moves from position 2 into position 3,an energizing circuit for the relay 99 is closed by way of spring 151top (Fig. 5) and spring 152 bottom (Fig. 2). This is a locking circuitfor the relay 99 and remains closed until the controlling equipment hasestablished the desired connection, or until the operator at clears outthe circuit.

It was assumed that equipment A was idle. If equipment A had been busyand sprin-g 98 top had been closed, the circuit through sequence switch305 and relay 99 of the B havel been opened immediately at left backcontact of relay 99, and hence the position sequence switch 305 wouldhave remained at position 7.

Itshuld be here observed that if the connecting circuit had been inconnection with the alternateoperator, that is, with the position.sequence switch in position 3 instead of position 7, a similar testingof the controlling equipments of such alternate operator would havetaken place over spring 74 bottom and spring 73 bottom. In that case, ifthe A equipment had been idle, rthe position .sequence' switch wouldhave been driven to position 5 and such A equipment placed inco'perative relation to the connecting circuit, whereas, if the vA'equipment had been busy, the position sequence switch would haveremained in position.V 3 and the B equipment so associated. From thispoint on the operation is precisely the same whichever operator theconnecting circuit is connected with, and whichever equipment of suchoperator is in controlling relation therewith. In all cases when thedesignation of the desired .line has been completely recordeid on theoperator-s keys Fig. tion .sequence switch will be advanced oneposition, to lopen the connection to the operators telephone and uponthe completion 'of the selection-controlling operation the positionsequence switch will be operated (through the group sequencev switch) tomove into itsv eleventh position,-all of which will be hereinafterdescribed,.such operation taking place regardless of the position theposition .sequence'switch may be iny at that time, that is to say,regardless of which of the various equipments may have been connectedwith the connecting circuit by such position Ysequence switch to controlselection.

The apparatus is now ready for the registration of the designation ofthel desired line, and, in accordance therewith, to control the movementof the various switches to connect with the terminals of the requiredsubscribers lin-e. The operator having received the number desireddepresses the corresponding keys of the sets of keys shown in Fig. 6.

There is arranged a key -for each digit, there being ten units keys, tentens keys, ten hundreds keys and ten thousands keys. It may be notedthat each row of keys is provided with a holding magnet 290, 291, 292,293, each arranged to hold depressed the depressed key of its row. Thecircuit of these magnets is closed -by Way of the spring 294 (Fig. 5)when the equipment sequence switch isin positions 3 to 7, a specialreleasing key 295 being included in the circuit of the holding magnetsto release -the keys if, before the designation of the desired line iscompletely recorded, the operator should observe that yshe had depresseda wrong key. In depressing `the digit keys, the operator depresses theunits key last. When the units key is depressed an energizingcircuit'for the equipment sequence-switch 505 is closed to move it intoposition 6', such circuit 'including the contact on the units key,spring 153 top and spring 154 top. As the sequence switch moves fromposition 3 ,into position 4, an impulse is transmitted to the groupsequence switch 205 over a circuit through spring 1.55"(Fig. 5), spring.

and spring 157 top it "into position 4.,

156 bottoI.ri.(Fig. 2), (Fig. 2) to move As it moves from position 3, animpulse is sent to the position sequence switch 305, over spring 158 topand spring 159, driving it out of the 9th or operators listeningposition and into position 10. In this position the A equipment of thehome position is still connected to' the circuit, but the operatorstelephone set is disconnected from the circuit at spring bottom andspring 91'bottom, and also the holding circuit 'of the relay 82 of thehome operator (Fig. 4) is opened at spring 88 bottom (Fig, 2). Therel-ay '82 of the home operators sequence switch becomes denergized,closing a circuit over spring 81 bottom, to drive the home operatorssequence switch to its normal position and render it free to beconnected to `other lines to which calling subscribers may be'connected.

4The selection controlling equipment is now ready to control theestablishment of the connection.

yAs'the units key of the keyboard was depressed, the same circuit whichresulted in the movement of the equipment sequence switch formed a partof circuits established for the various power magnets 160, 161, 162 and163 of the 10.00s, lOOs, lOs and units registers respectively inparallel by way of spring 153' and the Contact on the units key to earthas above described. These registers rotate until the positioncorresponding to the depressed key of its -associated set of keys isreached, where the circuits through their power magnets are broken bytheir respective test relays .170, 171, 172, 173. `For example, if thenumber four, the fifth, tens key has been depressed the tens registerwill v be' driven by the energization ofitsv power magnet 162 until itcomes into its position 4 when a circuit will be closed through thenumber four tens key through the register spring, of the upper set ofiive springs of such register, adjacent to which the number 4 is placed,and test relay 172. The energization of the test relay by this circuitopens the circuit ofthe power magnet 162 and brings the tens register toa stop in its number four position, whether the other registers arestill in motion, vor where they may stop. It should be noted that forthe sake of clearness the ten positions of the registers are numberedfrom zero to nine to agree with the designation of the keys by whichthey. are controlled. That is to say, when the zero key has beendepressed, the corresponding register will move into its zero position,and all of the switch springs of such register designed to be closed inits zero positiomthatA is, all that have the ligure zero placed adjacentthereto, will be closed and remain closed until for the control of asubsequent connection the register is again moved. In this manner,therefore, all of the registers lare simultaneously set to register orrecord the designation of the ,desired line as recorded by the operatoron her setor` keys,

' 'and such keys may then be released to control registration in the Bequipment of the same operatorv such release taking place when theequipment sequence switch moves out of its seventh position.

With the group sequence switch 205 in position 4 the position sequenceswitch 305 in position 10, the equipment sequence' switch 505 inposition 6, the fundamental or selecting circuit from the A equipment(Fig. 5) to the group selector 300 (Fig. 2) is ,completed, thisselectingv circuit being as follows earth, spring 15S bottom of thegroup sequence switch, spring 164 bottom of the position sequenceswitch, back contact of relay 165 (Fig. 5), winding of selecting re.

lay 166, spring'167 of the equipment sequence switch, spring 168 bottomof the position sequence switch, spring 169 bottom of the group sequenceswitch, line relay 174, spring 175 bottom to battery. Relays 166 of theselection-controlling equipment, and line relay 174 of the groupselector are thereupon energized. Relay 174 closes a circuit over spring176- bottom, which drives the group sequence switch from position 4 intoposition 5, in which position the fundamental circuit remains unchangedand a circuit is closed over spring 177 top to the power magnet 312 ofthe brush chooser of independent of,

'sixth level on the group switches.

' vancing stage of the brush choosing mechanism the interrupter 17 Scloses a low resistance path to ground which shunts out theselecting-relay 166 (Fig. 5) but maintains energized the line relay 174of the group selector.

The armature of the selecting relay 166 of the sender circuit thereforefalls back and is attracted once for each step taken by the brushchoosing'device. Referring to Fig. 5, as the relay 166 is energized, foreach closing of its front contact, a relay 179 of the upper countingrelays is energized by way of the left back contact'pf the correspondinglower counting relay 180 and spring 181, whereas for each time relay 166closes its back contact, one of the lower the front contact of thecorresponding upper counting relay 179 and spring 182. These countingrelays, when once energized, lock themselves over their own right frontcontacts and springs 181 and 182 respectively, and the circuits for thesecond and subsequent relays of both the relays 179 and 180 will'beestablished over such ofthe relays as have been locked up. as will beplainly apparent from yan examination of Fig. 5.

One counting relay after another is energized, first a relay 179,' thena relay 180` then a relay 179, and so on until that pair of countingrelays is energized corresponding to the closed register switch springsof the hundreds and thousands registers (as determined by the depressedkeys in the keyboard). g,

The selectors used in this systeml are. 200- line selectors so that itis necessary to translate from a decimal system to a system that isnon-decimal, corresponding to the grouping of the lines in the switches.The operator, when registering the call, depresses keys vcorrespondingto the 1000s, .100s, 10s, and units digits of the desired line, that is,on a decimal basis.

Inasmuch as 200 lines are connected to the final selectors in eachgroup, it follows that each level of terminals in the group selectorgives access to a group of 200 lines. The first levelgives access tolines numbered 0-199, the second level 20G-399, the third level 40G-599,andl so on. If it be assumed that the required number is 1149, thetrunks leading to the final selectors containing this particular line.are wired to the Consequently, the group selector brush-Chooser mustmove six steps or stages to selectthe proper set of brushes, whichmovement will result in the energization and denergization of thestepping relay 166 six times.

In response to the action ot the operator in ldepressing keys in therespective sets to the 1005 register will be 'closed at the top(position 1). The 10s register will have its spring 185a closed at thetop (position 4) while the units register will have its springs 183b and192b each closed at the bottom (pof sition 9).

Y'Vhen the sixth shunting of the stepping relay 166 is caused by thebiush-chooser of the group selector, the siXth lower counting relay 180was energized, and a circuit was closed, over right hand front contactof the sixth counting relay 180, contact spring 196 bottom of `the 100sregister, contact spring 191 top of the thousands register, spring 188bottom of the equipment sequence switch, andlthrough relays 190 and 165.Relay 190 energized closesa circuit to the power magnet 505 over spring154 bottom, and the equipment sequence switch moves into position 8, inpassing through position 7, opening springs 181 and 182, allowing thelocked l counting relays to be denergized. As it leaves its seventhposition it opened the springs 153 and 294, the spring 294 opening' lthecircuit of the holding magnets 290, 291, 292, and 293, of the severalsets of keys and the depressed key in each set resumes its normalposition. Spring 153 opens the circuit over which the power magnets'160, 161, 162, and 163, of the registers were put in motion and rendersit impossible for the operation of the keys to affect the positions ofthe registers shown on Fig; 5 so long as 'the' selection-controllingoperation is going on. It will thus be seen that though the set of keysmay now be associated with the equipment B of the operator by springsperformingv precisely the functions of the springs 153 and 294 and, asindicated by the multiple conductorsshown on Fig. 6, so be used tovcontrol the selection-controlling operations of such equipment B inconnection with-some other call, no operation of these keysc-an in anyWay interfere with the selection-controlling operations now going ou inthe equipment A.

With the sender sequence switch in position 8,the selecting circuit isagain closed at the controlling equipment for governing selection.according to the 10s digit ofthe wanted line.

When at position 6 'of the equipment `sequence switch, the relay 165 wasenergized it immediately opened the fundamentalcircuit to the groupselector including the line relay 174 (Fig. 2), which relay, when thebrush-Chooser has nished its siXth step .or stage and the shunt to earthis opened, will be denergized, opening the power circuit to thebrush-Chooser, causing it to stop in its sixth position and also closesa circuit to the group sequence switch 205 over spring 176 top, so thatsuch switch moves into position 6. This is the trunk hunting positionfor the group selector 300. The third or test brush 303 of the groupselector is connected through left hand (high resistance) windingA 0fthe test relay 198, spring 69 top, test relay 199, normally closed4contact of locking `key 68, left hand back Contact of relay 67 to earth.The brushes of the group selector are rotated due to the closure of acircuit from brush-carriage power magnet 306, over spring 250 bottom,and back contact of relay 199. As the test brush 3032L touches a testterminal 303 of a trunk line of an idle iinal selector, upon whichterminal there is present the full potential of the battery connectedover spring 253, spring 275', relay 2531, and back contact of relay 283,the test relay 198 will be energized, placing' its low resistance righthand winding parallel to its high resistance left hand winding, therebyclosing a. low resistance path to the third terminal of the trunk andmaking it busy by lowering its potential. As soon as the brushes havebeen accurately centered upon the trunk. the shunt through theinterrupter device 286 is removed and relay 199 lis also energized,which opens the circuit of the power magnet 306. and closes the circuitto the holding magnet 310, causing the brushcarriage instantly to stoprotating. The energization of relay 199 also by a circuit over spring157 bottom' drives the sequence switch 205 into position 7.

In this position the fundamental or lselecting circuit is again closed,this time to the bru-shes 30121, 302% at spring 251 bottom and spring 252 bottom, and thence to the final selector 600 by spring 253 bottom toearthon the one hand, and spring 254 top through the line relay 255 tobattery on the other. Relay 255 (Fig. 3) and relay 166 (Fig. 5) are tereupon energized, and the former closes .f n energizing circuit `forthe tinal sequence switch 605 over springs 257 top and 256 bottom tomove it into position 2, in which position the apparatus is in conditionto select the set of brushes in the final selector according to the tensdigit of the numbei of the desired line. As the sequence switch movesinto position 2 a circuit for vthe brush-choosing power magnet is closedthrough spring 256 bottom, front contact of relay 255, and spring 258top. For each step taken by the brush-choosing mechanism the interrupter259 closes a low resistance path to earth over spring 260 top in shuntergization of the selecting relay 166 causes it to lock up the countingrelays, as has been described infconnection with the selection 4of. thedesired llevel in the group selector.

Since wehave assumed that the required number was 1149, the contact185El top of the s register is closed and the fifth lower countingrelay, upon being energized, closes a circuit over its right armature,register spring 185 top of the 10s register, sequence switch spring 188top, and relays190 and 165. The energization `of the relay 190 by thiscircuit causes the equipment sequence switch 505 to advance to position10 and the -energiza-tion of the relay 165 opens the selecting circuit,as explained above. As the equipment sequence switch passes throughposition 9, it unlocks the counting relays allowin them to assume theirnormal positions. Vhen the fundamental' circuit is opened atthis timetherelay 255 (Fig.'3) becomes dependent for its energization on theconnection to ground through the interrupter 259 and when thebrush-Chooser com-4 pletes its fifth step or stage of movement, thisconnection being open, the relay 255 is denergized and closes a circuitover spring 256 bottom, and spring 261 top,`.for the final sequenceswitch, moving it into the fifth position. In this position and with theequipment sequence switch in the tenth position the fundamentalcircuitis complete as before for controllin the iinal selection at theline switch 600. Vhen the equipment sequence switch closes thefundamental circuit at position 10, the final selector line relay 255(Fig. 3) is again energized, closing a circuit over spring 256 bottom,and spring 262 top for brush-carriage power magnet 606. n

As the brush-carriage passes the tripping spindle `of the brush-Chooser,the selected set of brushes having access to the desired level(containing those havin the tens digit of thewanted line) is trippe andfor each set of terminals in this level alow resistance path to groundis closed at the interrupter 263 to the battery side ofthe fundamentalcircuit over spring 263 top, 'contact springs actuated by arms 263, andspring 260 top. As in the selection of the tens level, the selectingrelay 166 (-Fig. 5) is alternately energized and denergized, with theconsequent locking up bf the counting relays, the line relay 255remaining continuously energized. The final selectors are 200-"linemachines, having 10 levels of 20 lines each. The first ten sets ofterminals of each level correspond to the even hundreds'of 'each group,while the second ten sets of terminals correspond to the odd hundreds ofthe group. The par- 'l ticular line we are considering is 1149V andsince the lowest level is occupied by numbers whose tens 'digit iszeronthe line we are considering lies in the fifth level. The particularunits digit of this line appears in .i the lsecond set of ten in thislevel, inasmuch as its 100s digit is odd. The spring 197 of the 100sregister is closed at thetop and will consequently connectinto circuitthe units register Springs 192i, 193D, 1941 19511, 19th, keeping open at197 bottom the circuits of the units'register .springs 183), 1851, 186",187". Consequently, not until the twentieth counting relay has beenenergized,will"the circuit be closed over right armature and frontcontact of the twentieth relay v180, units register spring 1'92b bottom,100s register. spring 197 top, equipment sequence switch' spring 189 andrelays 190 and 165. Relay 165 opens `the fundamental circuit, and causesthe re-A lay 255 (Fig.v 3), when the brushes are properlycenteredand theshuntthrough the in- (Fig. 5)l which was started by the energization ofthe relay 190 moves from position 10 through position 11, an impulse istransmitted to the group .sequence switch 205 over spring 155 (Fig- 5),spring4 156 bottom (Fig. 2), and spring 157 top (Fig. 2). This movesthegroup sequence switch into position 8, in which movement-a circuit isclosed to' the position sequence switch 305 over spring 158 top andswitch spring 159., sending the position sequence switch into position11.

99 (Fig. 5) at its spring 152 bottom and relay 99 (Fig. 5) becomesdenergized, lclosing'a circuit over spring 150 bottom, to drive theequipment sequence switch to its normal positionv and entirely freeingthe registering and' controlling equipment A so that it may be used tocontrol selection in settlng up another connection.

It may be notedl that the equipment sequence switch 505 -c oses inposition 6 over spring 296 a circuit for the progress lamp297, thislighting of the lamp indicating that 'the first selection, that is, tlieselection in the group selector, `is taking place properly. Similarly inthe positions 8 and 10 of the equipment sequence switch, circuits forthe progress lamps 299 and 350 are closed over spring 298 top and bottomrespectively, these lamps indicating that the tens and final selectionsareoccurring.

.As the position sequence switch 305 moves into position 11, springs156, 168, 164, and

The position sequence switch in l position 11 opens the holding circuitto relay

